There is recent evidence that the immune response may play a role in the central nervous system during embryogenesis, neonatal development, normal healthy adult life, trauma, and disease. Leukocytes regularly traffic to and from the brain and secrete cytokines which can alter the morphology and function of resident glial cells. Primary myelination and remyelination after trauma/disease are probably mediated by the oligodendrocyte or its precursor, both capable of proliferation and differentiation. We have recently identified, purified, and characterized a T lymphokine from Mo cells, glial growth promoting factor (GGPF), which is one of the first glial specific lymphokines to be described and the first such factor shown to be specific for oligodendrocytes. With this technique we can purify large amounts of natural GGPF necessary for the generation of antibody and primary amino acid sequencing. In addition, we are screening a Mo expression cDNA library for recombinant proteins that stimulate oligodendrocytes to proliferate. This is the same technique that was used to clone human granulocyte-macrophage colony stimulating factor (GM-CSF). We wish to obtain cDNA clones encoding GGPF and use purified natural or recombinant GGPF for further biochemical and biological characterization. The Mo expression library consists of cDNA inserts in the 91023(B) expression vector which are transiently transfected into COS monkey kidney cells. Once we have isolated cDNA clones encoding GGPF, confirmation of the biochemical identity of natural and recombinant GGPF will be by a nucleotide and amino acid sequence comparison, molecular weight comparison, and binding of recombinant GGPF by anti-natural GGPF antibodies. Biological characterization will assess proliferation of primary neonatal and adult rat and human oligodendrocytes, induction of differentiation, and remyelination in cerebellar explant cultures.